Method and system for measuring the distribution of the energy field density of a laser beam

ABSTRACT

A method and system for measuring the distribution of the energy field density of a laser beam is provided. Laser pulses of the laser beam are extracted in groups or individually from the laser beam, are locally separated from one another, and the respective distribution of the energy field density of the deflected and locally separated individual laser pulses is measured.

BACKGROUND AND SUMMARY OF THE INVENTION

This application claims the priority of German Application No. 198 22924.0, filed May 22, 1998, the disclosure of which is expresslyincorporated by reference herein.

The invention relates to a method and system for measuring thedistribution of the energy field density of a laser beam, as well as toa system for implementing the method as used in the laser technologyfield which is widely known.

To measure a laser beam requires the measurement of a large number oftime-related and site-related beaming data. The measurability as well asthe informational value of these data depends largely on the beam sourcewhich is used. With respect to the laser, a differentiation must be madebetween pulsed operation (p) and continuous-wave operation (c_(w)).Furthermore, in the case of pulsed operation, the pulse duration t_(p)and the pulse period T or the pulse frequency f_(p)=1/T must beconsidered to be largely independent values. In contrast to pulses,which are generated by acousto-optical modulators (Q-switch), in thecase of lamp-pulsed systems, the above-mentioned values are mutuallydependent to a high degree.

The distribution of the energy field density or intensity in the planeperpendicular to the propagation direction of the laser beam I (x, y) isan important measurable variable during the lasering of material. Withrespect to its lateral distribution, this measurable variable isresponsible for the symmetry of the ablated workpiece volume(particularly important during the laser drilling and removal process).The energy flux density, which in a first approximation is responsiblefor the removed material volume, can be calculated as the product of theintensity and the pulse duration.

It should be noted that measuring such an intensity distribution shouldbest take place in focus or close to focus (I^(focus) (x, y)) There aretwo important reasons for this: (1) possible additional disturbancevariables (lens, deviation mirror, thermal refractive effects, phasefront deformations . . . ) are included in the measurement; and (2) thisselection of the measuring site also makes it possible to directlymeasure geometrical beaming data (focus diameter d_(f), beaming quality,beam position, . . . )

Currently, measuring instruments are available on the market for only afew measuring tasks (CO₂-laser, cw-operation) Particularly in the caseof fast and short-pulsed lasers, virtually no adequate measuringinstrument is available. Mainly within the wavelength range of 1,064 nmand 532 nm (Nd:YAG), CCD-cameras are used as site-resolving sensors. Formeasurements in focus or close to focus, systems are used which arebased on the principle of a rotating needle or rapidly moving screens.However, the above-described measurable variables can be sensed by meansof such systems only in a few exceptions. In particular, the transversalintensity distribution of Nd:YAG lasers in focus or close to focus:I_(focus)(x, y), cannot be measured by the offered instruments.

The only systems which can manage the high power densities of thelasering focus (rotating needle or similar devices) have, among otherthings, an insufficient site resolution for the wavelength of the Nd:YAGlaser. In addition, this method is basically unsuitable for pulsedlasers because the measurement of an intensity profile is composed ofmany partial measurements of different pulses.

For measuring laser pulse groups (hereinafter a laser pulse group isdefined as a number of several directly successive laser pulses) andindividual laser pulses, CCD cameras or similar site-resolving sensorsare particularly suitable. This is because these can record an intensitydistribution in a measuring operation. However, these systems, which arebased on CCD-sensors, so far have no suitable triggering possibility forrecording individual laser pulses. In addition, with the exception ofvery costly high-speed cameras, they are unable to record successivelaser pulses. CCD cameras, as they are partly used in beam diagnosticmodules, operate at 25-60 Hz. Based on normal frequencies of laserpulses (percussion drilling 10 Hz-10 kHz), an integration takes place inthe extreme case by way of a laser pulse group of approximately 150 to300 individual laser pulses. In addition, none of the CCD diagnosticsystems can be used in focus or at least behind the lasering lenssystem.

It is an object of the present invention to develop a method and systemby which the above-mentioned disadvantages are, at a minimum, reduced.

This and other objects are achieved by a method for measuring thedistribution of the energy field density of a preferably pulsed laserbeam, characterized in that a measuring beam which is correlated withthe laser beam particularly in a constant manner is extracted from thelaser beam. The measuring beam is imaged at different points in time ina defined and locally mutually separated manner. The distribution of theenergy field density of the time-resolved partial beams of the measuringbeam, which are imaged in a locally defined manner, is measured. Asystem to implement the method has a laser source and a detector whichat least partially detects the distribution of the energy field densityof the laser beam. The system has an extraction device (beam splitter)for the at least partial intensity-side extracting of a measuring beampreferably constantly correlated with the laser beam, from the laserbeam. The extraction device is arranged within the beam path of thelaser beam. The system has a deviating device which is arranged in thebeam path of the measuring beam. The deviating device has at least onemanipulator which, as a function of the time, deflects the measuringbeam into defined directions in space and divides it into variouspartial beams, for example, a mirror which is controlled by means of arotary step motor. The detector is arranged in the area of partial beamsof the measuring beam which are deflected by the deviating device.

In addition to achieving the above object, the present invention alsohas the following advantages:

(1) It characterizes the laser beam sources as well as time-relatedbeaming characteristics;

(2) By means of the improved time-resolved measurement of a pulsed laserbeam, informationally valuable data can be obtained for the processsimulation (laser drilling/laser removal);

(3) A process monitoring (on-line) is possible for quality controlduring manufacturing operations with pulsed beam sources, particularlyin the case of laser ablation, laser drilling and/or laser weldingprocesses; and

(4) Systematic and/or statistical machining defects can be diagnosed andanalyzed more precisely because, by using an informative beam diagnosis,it can clearly be decided whether the defects originate fromfluctuations/defects of the material or from fluctuations asymmetries ofthe beaming source.

With respect to all fields of laser machining, it is generallyapplicable that the method according to the invention and the systemaccording to the invention can be used in a simple manner, preferably inmanufacturing and production. In particular, the beam diagnosticpossibilities according to the invention are easy to operate and caneasily be adapted. It is also a special advantage that, during ameasurement in or behind the machining focus, no intervention isrequired in the beam guiding of the machining equipment.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a schematic block diagram of the construction of equipment formeasuring the laser intensity in the machining beam path of the laserbeam according to the invention;

FIG. 2 is a schematic block diagram of the construction of equipment formeasuring the laser intensity in a beam path coming from the toolaccording to the invention; and

FIG. 3 illustrates a measuring result of a time-resolved andspace-resolved beaming of a laser.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a concrete construction for measuring thedistribution of the energy field density of a laser beam while using asystem according to the invention which will be described in detail inthe following. The illustrated system covers all above-mentionedfunctions. The elements of the standard equipment of the constructionare listed in Table 1; optional expansion possibilities are indicated inTable 2.

TABLE 1 Components of Standard Equipment of the System Tab. 1Components/Function Option 1 Machining lens system of Imaging lenssystem replaces laser system in the case of machining lens system in thefocus diagnosis case of crude beam observation 2 Machining and imagingfocus 3 Widening/focussing lens for beam collimation 4 Beam splitter forattenuation. In transmission, a power Possibly additional beam measuringdevice (12) can splitters. be operated for calibrating the system. 5Variable attenuator Attenuation factor 0-10⁻⁵, by means of neutral wedgefilters, filter wheels or similar devices. 6 x/y scanner + control unitAlternative: Polygonal mirror or similar device. For a furtherattentuation of the beam, the scanner mirrors can also be provided withan AR coating. 7 Imaging lens 8 CCD camera or measuring sensor(site-resolving) 9 PC + interface modules For a standard product, toperiphery central control and handling unit and video screen alsosufficient.

TABLE 2 Components of Expansion Possibilities of the System Tab. 2Components/Function Option 10 Shutter for recording Chopper controlledpulses of long pulse duration (triggering by photodiode at 12.1) orc_(w)-lasers. 11 Z-positioning for adaptation When the scanner is of thespot size with respect inoperative or removed, to scanning rate. thebeaming quality can be measured according to DIN by displacing the lens.12 Power measuring device + measuring head for calibration can be readout directly by PC for beam position and beam quality measurement.

Additional optional components are, for example, elements whichattenuates the laser beam. With respect to their type and theirfunction, these components are dependent on the power of the laser to bemeasured. The special selection and sequence of the components should beadapted to the respective application case (type of laser, power oflaser, wavelength, etc.).

The actual system for measuring the distribution of the energy fielddensity of the laser beam comprises a variable attenuator 5, a deviatingdevice 6, an imaging lens 7, a detector 8 with a site-resolvingmeasuring sensor 14 and an apertured diaphragm 10 which can be openedand closed in a controlled manner for a lock-in process for reducing andsuppressing noise. The two optical elements 6.2 and 6.3 form a so-calledx,y-scanner for the defined deflection of the laser beam in the x- andin the y-direction. Together with the control unit 6.4, they form thedeviating device 6.

The laser beam coming from the laser, which is not shown, in the case ofthe focus diagnosis illustrated in FIG. 1, is imaged by the lens 1 of amachining lens system of the laser system by way of a machining orimaging focus 2 onto a collimation lens 3 for the beam collimation. Thecollimation lens 3 may be a widening or focusing lens or a correspondinglens system.

In the beam path of the laser beam, one or more beam splitters 4 arearranged behind the collimation lens 3. The beam splitter 4 splits theoriginal laser beam into a measuring beam 2.1 and a continuous beam.

The beam splitter 4 can attenuate the continuous laser beam, in additionto the intensity of the laser light split-off by the beam splitter 4.This is particularly useful if the continuous laser beam is guided to apower measuring device 12.1 with the measuring head 12. Here, themeasuring device 12.1 can be read out directly by a PC 9 in the case ofa beam position and beam quality measurement for calibration.

The split-off laser beam, thus the measuring beam 2.1 which iscorrelated in a preferably fixed relationship with the laser beamprovided, for example, for laser machining, passes through the variableattenuator 5. The attenuator is used particularly for protecting thephotodiode arrays of the future CCD camera used as the detector 8. Theattenuation factor of the variable attenuator 5, which is preferablycarried out by using neutral wedge filters, filter wheels or similardevices, can be varied here between 0 and 10⁻⁵.

In the beam path of the measuring beam 2.1, the attenuator 5 is followedby a deviating device 6, by which conditions which differ with respectto time, thus particularly individual pulses or pulse groups and thetime sequence of the measuring beam can be imaged in a defined manner atspatially different sites.

For this purpose, the deviating device preferably has a so-called x/yscanner, which is known particularly from the laser inscriptiontechnique and which has two mirrors 6.2. and 6.3. as well as apertaining control unit with a step motor 6.4. Instead of the mirrors6.2 and 6.3, so-called polygonal mirrors or similar devices can also beused. Furthermore, the scanner mirrors for the further attentuation ofthe measuring beam 2.1. can also be provided with an AR coating(anti-reflection coating).

For imaging the pulses or pulse groups of the previous measuring beam2.1., which were time-resolved in a defined local manner, onto asite-resolving measuring sensor 14, such as a photodiode array of a CCDcamera used as the detector 8, another imaging lens 7 is arrangedbetween the measuring sensor 14 and the deviating device 6. By means ofthe imaging lens 7, the spot size of a pulse or of a pulse group of themeasuring beam 2.1 can be adapted to the scanning rate.

In particular, by displacing the imaging lens 7 approximately inparallel to the propagation direction of the pulses or of the pulsegroups, the beaming quality can be measured according to DIN. However,for this purpose, the deviating device 6 must not be active so that themeasuring beam 2.1. is not deflected in a locally defined manner andtherefore time-resolved.

The displacement of the imaging lens 7 takes place via a carriage 11which can be driven by a linear step motor 11.1. Control of the motor isby an electronic system 11.2.

The system also has a so-called “chopper” (a movable, particularlyrotating apertured diaphragm 10) which is arranged in front of the beamentrance of the measuring beam 2.1. processed by the deviating device 6into the CCD camera used as the detector 8. By means of the chopper,very long laser pulses (>ms), for example, from cw-lasers, can bechopped into individual pulses for measuring.

Finally, the system also has a computer 9 with pertaining interfacecards to the corresponding control units and to the laser (FIG. 2, line17), by which the whole process can be documented and, whencorresponding software can be automated.

In practicing the method of the invention, the machining focus of thelaser beam is preferably imaged on a CCD chip. By using an x/y scannerin the deviating device 6, the time sequence of the laser and/or heatradiation, which can be used as the measuring beam 2.1, or of thecorresponding pulse groups of the measuring beam 2.1. is locallyresolved; that is, in particular individual pulses are imaged on the CCDchip side-by-side. By means of this method, measuring frequencies can,for example, be reached which are even higher than 10 kHz. Asillustrated in the expanded view of FIG. 3, at 200 pulses per videoimage, this value corresponds to a single-pulse field of approximately70×70 pixels, in which case a detector surface with 1,000×1,000 pixelswas used. The course of the recorded distribution of the energy fielddensity can then be determined from this image in a simple manner byintegration. It can also be displayed in an energy field density—timediagram 13 and can optionally be correspondingly analyzed, as describedbelow by way of Examples 1 and 2.

As the result of the free programmability of the scanner, allfrequencies from 0 to 10 kHz can be selected almost continuously withthe corresponding resolution (full image up to 200 pulses per frame).

In the following, several advantageous characteristics of the inventionare summarized as examples:

(1) Measuring of pulse chains to (f_(p)>10 kHz) in focus or in the crudebeam;

(2) The conventional x/y scanner can be freely programmed with respectto its movement;

(3) The imaging and frequency scale is freely selectable;

(4) A modular construction is possible:

(a) Alternative use in crude beam or focal area;

(b) fast, advantageous retooling is possible;

(c) shutter/chopper optional for long pulse durations or in thecw-operation;

(5) By means of an additional movable lens 7, the beam position andcaustic surface can be measured according to DIN EN ISO 11146; and

(6) The development expenditures are low because only standardcomponents are used.

The diagnostic concept is suitable for measuring and monitoring tasks onmaterial machining lasers, particularly when the invention is used forpulsed Nd;YAG systems for drilling and ablating workpieces.

Virtually all pulsed laser systems can be monitored and measured bymeans of this principle so long as locally high-resolving detectors areavailable for the wavelength ranges.

However, the system is particularly suitable for lasers which work inthe cw-operation. In this case also, sampling rates of 10 kHz can beachieved for the first time when measuring intensity distributions.

Furthermore, this method can also be used for observing reflexes fromthe machining zone. By means of a corresponding imaging lens system, thesame construction can also be used for a 10 kHz process diagnosis.

FIG. 2 shows another construction for measuring the intensity of a laserbeam according to the invention. The system according to FIG. 2 alsocovers all functions mentioned above. Since the construction of theequipment according to FIG. 2 is largely identical to the constructionaccording to FIG. 1, only their differences will be discussed here.

In contrast to the construction of FIG. 1, the mirror used as a beamsplitter 4 is rotated 180°. As a result, no portion of the laser beamcoming from the laser is extracted as a measuring beam 2.1. On thecontrary, radiation is now used as the measuring beam 2.1. which comesfrom the workpiece and is the result of the machining laser beam. Inparticular, this is the laser beam reflected by the workpiece 15 and/orheat radiation coming from the momentary machining point of theworkpiece 15.

The further processing of a measuring beam 2.1. corresponds to thatdescribed by means of FIG. 1. Since the measuring beam 2.1. may be heatradiation and/or a laser beam, differences may occur concerning theindividually used components. For the same reason, it is conceivablethat two measuring beams and therefore also two measuring paths areused, in which case one measuring path is then used for the heatradiation and the other is used for the laser radiation.

In the following, two different embodiments of the invention aredescribed. Both embodiments, which are implemented by a construction ofequipment corresponding to FIGS. 1 and 2, relate to the documentationand/or the monitoring of a working process in which a laser beam is usedparticularly for ablating, drilling or welding.

EXAMPLE 1 (FIG. 1)

By means of Example 1 described in the following, a documentationprocess is described, as can be used particularly during laser drillingand during laser welding. However, in contrast to FIG. 1, no powermeasuring device 12.0 with a measuring head 12.1, as illustrated, issituated in the impact area or at the machining site of the non-deviatedlaser beam, but, as illustrated in FIG. 2, the workpiece 15 to bemachined is located there.

During laser drilling, it is advantageous with respect to thecorresponding documentation to know which energy and therefore whichdrill-hole-related total energy is required for each drill hole 16.During laser welding, it is expedient for the laser weld seam to bestep-controlled and a corresponding progressive, thusweld-seam-length-related total energy of the laser beam is required.

For a preferably used pulsed laser beam, the total energy is formed bythe sum of the individual energies of the respective laser pulses. Inthis case, it should be taken into account that a portion of the energyentered by the laser may, under certain circumstances, flow off into thematerial of the workpiece to be machined.

In Example 1 according to FIG. 1, a defined portion of the laser beam isextracted as the measuring beam 2.1 from the focused and collimatedlaser beam 2 by means of the beam splitter 4. In this case, it isexpedient that the extraction remains the same at all times, whereby aconstant and simple correlation exists between the measuring beam 2.1.and the continuous laser beam. As the result of the extraction ratiobetween the measuring beam 2.1. and the laser beam (and possiblysubsequent attenuations of the intensity of the measuring beam 2.1.),the intensity of the continuous laser beam—therefore of the laser beamwhich was not extracted and is used for the machining—can be determinedin a simple manner.

The measuring beam 2.1. is processed in the above-described manner andthe distributions of the energy field densities on the detector 8 aremeasured and are documented particularly by means of a computer 9 or thediagram 13.

By analyzing the time-resolved individual pulses or pulse groups of themeasuring beam 2.1, it may now be determined that the sum of theindividual intensities of the corresponding laser pulses—thus the totalenergy required for the machining point —was too low or too high (forexample, drilling-through) for faultless machining operation. In thiscase, the produced workpiece will be defective. A simple and efficientpossibility is therefore implemented for monitoring the quality of amachined workpiece.

If, in addition to the distribution of the energy field density, thepertaining machining site is also recorded and documented, it can thenalso be quantitatively determined where a corresponding aftertreatmentof the workpiece is required and perhaps possible. By means of this moreextensive measure, the faulty site on the workpiece 15 can therefore bedetermined, whereby a method is provided for determining the location ofpossible subsequent machining. This reduces the costs of theaftertreatment because now a search for the faulty point does not haveto take place over the whole workpiece 15.

EXAMPLE 2 (FIG. 2)

By means of Example 2 described in the following, another documentationpossibility is described, as it can also be used particularly duringlaser drilling and laser welding.

In Example 2 according to FIG. 2, a defined portion of the radiationwhich comes from the workpiece 15 and is the result of the influence ofthe machining laser beam, is extracted as the measuring beam 2.1. by thebeam splitter 4 or optionally by a semi-reflecting mirror.

The measuring beam 2.1. is processed in the above-described manner andthe distributions of the energy field densities on the detector 8 aremeasured and documented. Since the measuring beam 2.1. is radiationcoming from the workpiece 15, particularly the backscattered laser beamand/or heat radiation, by means of the analysis of the time-resolvedindividual pulses or pulse groups of the measuring beam 2.1., aconclusion can be drawn with respect to the machining result.

Such an evaluation will be described in the following by means of adrilling operation 16 carried out by a laser beam. As long as the drillhole 16 has not yet been completely made, the time-resolved measuringbeam 2.1. exhibits at most a slight change between two successiveindividual distributions of the energy field densities. This change issituated above a definable threshold value. This applies, irrespectiveof whether the measuring beam 2.1. is now laser radiation or heatradiation.

When the drill hole 16 is now completed, the corresponding energy fielddensity of the measuring beam 2.1. falls below the threshold valuebecause the laser beam is no longer backscattered or is only slightlybackscattered and the heating at the machining site by means of thelaser beam is reduced.

If, in the case of a given number of laser pulses per drill hole 16, aquantitative analysis is now carried out, a conclusion can be drawn withrespect to the machining quality by means of the distribution of theenergy field density. Since, in the case of a completed drill hole 16,the distribution of the energy field density of the measuring beam 2.1.pertaining to a laser pulse now falls under the threshold value, threepossible cases exist:

a) The distribution of the energy field density of the defined lastlaser pulse falls below the threshold value. In this case, the drillhole 16 is good;

b) The distribution of the energy field density falls below thethreshold value before the defined last laser pulse. In this case, thewall of the workpiece 15 situated opposite the drill hole 16 may havebeen damaged. The damage may consist, for example, of another unintendeddrill hole made in this wall or of a thin point; and

c) Also during the last defined laser pulse, the distribution of theenergy field density does not fall below the threshold value. In thiscase, the drill hole 16 was at least not completed.

Here also, a simple and efficient possibility is implemented formonitoring the quality of a machined workpiece 15.

If, in addition to or instead of the distributions of the energy fielddensities, the pertaining machining site is also recorded anddocumented, it can then also be quantitatively determined where acorresponding aftertreatment of the workpiece 15 is necessary andperhaps possible. By means of this more extensive measure, the faultysite on the workpiece 15 can therefore be determined, whereby a methodis provided for determining the location of possible subsequentmachining. This reduces the costs of the aftertreatment because now asearch for the faulty point does not have to take place over the wholeworkpiece 15.

In an advantageous further development of the above-mentioned methodaccording to the invention, the respective distribution of the energyfield density, if possible, is analyzed without any time delay and isused for controlling the machining. In the case of the above-mentionedmachining example, this expediently takes place in that the drilling bymeans of the laser beam takes place until, at the site-resolving sensor14 of the detector 8, the intensity of an individual pulse falls belowthe threshold value. When this occurs, a timing operation until the nextdrill hole takes place. In a preferred manner, until the next drill hole16 is reached, the laser beam can be covered or the workpiece can beconveyed further and can be positioned correspondingly.

The method described by means of Example 2 is particularly advantageousin the case of workpieces which have a varying wall thickness course.

Preferred fields of application of the invention are the making ofcooling and form drill holes in the case of turbine blades, perforationsin the case of thin metal sheets, preferably for the boundary surfacesuctioning-off in the case of components surrounded by flows, such aswings and similar devices, injection openings of injection nozzles aswell as microstructures in sliding and running surfaces. On the whole,the method is also advantageous in the case of components which have apreferably stabilizing fluting or reinforcements on the interior side.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

What is claimed is:
 1. A method for measuring a pulsed laser beam'senergy field density distribution, the method comprising the acts of:extracting a portion of said pulsed laser beam as a measuring beam, themeasuring beam being constantly correlated with the laser beam; imagingthe measuring beam at different points in time in a defined and locallymutually separated manner to provide a plurality of time-resolvedpartial beams; and measuring the energy field density distribution ofeach of said time-resolved partial beams of the measuring beam, whichwere imaged in the locally defined manner.
 2. The method according toclaim 1, wherein the laser beam is a pulsed laser beam.
 3. The methodaccording to claim 1, wherein at least one of pulse groups andindividual pulses of the measuring beam are locally mutually separatedat different points in time, and further wherein the energy fielddensity distribution of the time-resolved pulses or pulse groups of themeasuring beam, imaged in a locally defined manner, is measured.
 4. Themethod according to claim 1, further comprising the acts of: reflectingthe laser beam off an object; and extracting the measuring beam from thereflected laser beam.
 5. The method according to claim 1, wherein themeasuring act further comprises the act of separately measuring from oneanother with respect to time the energy field density distribution ofindividual pulses or pulse groups of the measuring beam.
 6. The methodaccording to claim 1, further comprising the acts of: guiding pulses ofthe measuring beam to a deviating device and deflecting said pulses bythe deviating device in a locally defined manner; and adjusting adeflection of the deviating device per pulse or pulse group.
 7. Themethod according to claim 1, further comprising the act of mutuallyindependently deflecting the measuring beam via a deviating device intotwo different mutually transversely situated spatial directions.
 8. Themethod according to claim 1, wherein the measuring beam is guidedtransversely to an original propagation direction of the laser beam in adirection of a deviating device.
 9. The method according to claim 1,wherein radiation emanating from a machined workpiece as a result of thelaser beam is selected as the measuring beam.
 10. The method accordingto claim 9, wherein the radiation is heat radiation.
 11. The methodaccording to claim 1, wherein a reflection of the laser beam from amomentary machining site of a workpiece is selected as the measuringbeam.
 12. The method according to claim 1, wherein each pulse of themeasuring beam is deflected to a single point in space.
 13. The methodaccording to claim 1, wherein an individual pulse of the measuring beamis divided into several individual subpulses.
 14. The method accordingto claim 1, wherein the measuring beam is coupled out in an area of amachining focus of the laser beam.
 15. The method according to claim 1,further comprising the acts of: coupling-out the measuring beam from acollimated crude beam of the laser beam; processing the coupled-outcollimated crude beam in accordance with a future machining focus; andsupplying the processed collimated crude beam to a deviating device asthe measuring beam.
 16. The method according to claim 1, wherein themeasuring beam is coupled-out of the laser beam during a machiningprocess.
 17. A system for measuring an energy field density distributionof a pulsed laser beam, comprising: a laser source generating saidpulsed laser beam; a detector; an extraction device which extracts aportion of said pulsed laser beam to provide a measuring beam which isconstantly correlated with the pulsed laser beam, said extraction devicebeing arranged within a beam path of the laser beam; a deviating devicearranged in the beam path of the measuring beam, said deviating deviceincluding at least one manipulator which, as a function of time,deflects the measuring beam into defined spatial directions and dividesthe measuring beam into a plurality of partial beams; and wherein thedetector is arranged to receive the plurality of partial beams of themeasuring beam deflected by the deviating device to at least partiallydetect the energy field density distribution of the pulsed laser beam.18. The system according to claim 17, wherein the deviating device is amirror, and further comprising a rotary step motor coupled to controlmovements of said mirror.
 19. The system according to claim 17, whereinthe deviating device is a mirror movable in at least in one dimension.20. The system according to claim 17, wherein the deviating devicecomprises an optical deflector movable at least in one dimension, saidoptical deflector operating in a non-mechanical manner.
 21. The systemaccording to claim 17, wherein said deviating device comprises at leastone of a mirror, a beam splitter and a reflector.
 22. The systemaccording to claim 17, further comprising one of an optical switch andmodulator arranged in the beam path of the laser beam.
 23. The systemaccording to claim 22, wherein said one of the optical switch andmodulator is an apertured diaphragm disk rotating at a definedrotational speed.
 24. The system according to claim 17, furthercomprising one of an electro-optical switch and an electro-opticalmodulator arranged in the beam path of the laser.
 25. The systemaccording to claim 17, wherein said detector is a site-resolving sensorelement.
 26. The system according to claim 17, wherein said detector isa CCD camera.
 27. The system according to claim 17, wherein saiddetector includes a surface having site-resolving sensors.
 28. Thesystem according to claim 27, wherein said site-resolving sensors arephotodiodes.
 29. The system according to claim 17, wherein said detectoris a CMOS detector array.
 30. The system according to claim 17, furthercomprising at least one of focusing lenses, dispersing lenses, graydisks, mirrors and holographic-optical elements arranged in the beampath of the measuring beam.